feat(hermes): Hermes Agent harness support, rebased to a Hermes-only diff

Rebase of PR #1922 onto current dev: the ~14 files of v6.1.0-era
codex/release drift are dropped, the porting-guide edits (stale against
the post-prune rewrite, no Hermes content) are dropped, and the Hermes
surface is kept intact: .hermes-plugin/ (on_session_start bootstrap
injection), tests/hermes/ (20 tests, passing), docs/README.hermes.md,
references/hermes-tools.md, the Platform Adaptation row, README section,
and Python ignores.

Known open items from review, unchanged by this rebase: the injection
mechanism uses ctx.inject_message from on_session_start, which the
official plugin guide does not document (pre_llm_call returning
{"context": ...} is the sanctioned path), skills are not registered via
ctx.register_skill, and the acceptance transcript predates the fix.

Co-authored-by: kumarabd <kumarabd@users.noreply.github.com>

docs/README.hermes.md

@@ -0,0 +1,29 @@
+# Hermes Agent
+
+Superpowers supports Hermes Agent via an in-process Python plugin (Shape B).
+
+## Install
+
+```bash
+hermes plugins install obra/superpowers --enable
+```
+
+## What you get
+
+All Superpowers skills auto-trigger in Hermes sessions:
+brainstorming before feature work, systematic-debugging on bugs,
+test-driven-development for implementation, writing-plans before
+touching code, and all other skills in `skills/`.
+
+## How it works
+
+The plugin registers an `on_session_start` hook with the Hermes plugin API.
+At the start of each session, the hook injects the `using-superpowers` bootstrap
+as a user-role message via `ctx.inject_message(role="user")`. A session-id guard
+prevents double-injection if the hook fires more than once per session.
+
+Skills are loaded on demand during the session using `skill_view("skill-name")`.
+
+## Verifying
+
+See `.hermes-plugin/INSTALL.md` for the smoke check and acceptance test.